//渐变背景动画
.demo_1 {
    height: 100%;
    width: 100%;
    background-image: linear-gradient(145deg, rgb(6, 9, 202), orange);
    background-repeat: no-repeat;
    background-size: 300%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 30px;
    color: aliceblue;
    animation: bacmove infinite 10s ease-in-out;
    @keyframes bacmove {
        0% {
            background-position: 0 0;
        }
        25% {
            background-position: 50% 50%;
        }
        50% {
            background-position: 100% 100%;
        }
        75% {
            background-position: 50% 50%;
        }
        100% {
            background-position: 0 0;
        }
    }
}
